1. Field of the Invention
The present invention relates generally to a fuel control system for a multiple-cylinder internal combustion engine and particularly to a fuel cut-supply control system for an automotive vehicle by which fuel supplied into engine cylinders is automatically cut temporarily when the engine is being decelerated and supplied again when the engine is being accelerated.
2. Description of the Prior Art
There are will known some electronic fuel control systems for automotive vehicles which can economize fuel supplied into engine cylinders by cutting fuel temporarily or by reducing the amount of fuel only when the engine is being decelerated.
As a first prior-art fuel supply control system, there exists the one which comprises a fuel injection pulse generating section for generating a fuel injection pulse having an adequate pulse width in response to sensor signals indicative of engine speed and the amount of intake air, a fuel-cut determination section for generating a fuel-cut command signal in response to other sensor signals indicative of engine speed and throttle valve position, and a fuel-cut control section for allowing the fuel injection pulse to pass therethrough to fuel injection valves when no fuel-cut command signal is generated (when the engine is being accelerated) and allowing the fuel injection pulse not to pass therethrough to the fuel injection valves when a fuel-cut command signal is generated (when the engine is being decelerated).
In such a prior-art fuel supply control system, however, since the fuel is abruptly cut off from or resupplied into the engine cylinders when the engine is decelerated or accelerated, there exists a problem in that the engine vibrates excessively, thus resulting in poor riding comfort.
A more detailed description of this first prior-art fuel supply control system will be made hereinafter with reference to the attached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.
Further, as a second prior-art fuel supply control system, there exists an electronic fuel injection system, as disclosed in Japan Patent No. Showa 49-45648, which comprises a fuel injection pulse generation section for generating a fuel injection pulse having an adequate pulse width according to at-least one engine operating parameter, a switch closed when the engine is accelerated, and a monostable circuit triggered when the switch is closed and outputting a signal to adjust the pulse width of the fuel injection pulse outputted from the fuel injection pulse generation section, in order to increase the amount of fuel only when the engine is being accelerated.
In such a prior-art fuel supply control system, similarly, since the pulse width of a fuel injection pulse is abruptly increased for increase in fuel supplied into the engine cylinders when the engine is accelerated, there exists the same problem as in the first prior-art fuel supply control system in that the engine vibrates excessively, thus resulting in poor riding comfort.
Furthermore, as a third prior-art fuel supply control system, there exists a system of supplying fuel into engine cylinders, as disclosed in Japan Patent No. Showa 56-38781, which comprises a calculating section for generating a fuel injection pulse having an adequate pulse width in accordance with engine status, a fuel-cutting section for outputting a fuel-cut command signal when the engine is decelerated, and a fuel-resupply compensation section for generating a compensation command signal the level of which changes gradually after no fuel-cut command signal has been outputted, in order to gradually increase the pulse width of the fuel injection pulse outputted from the calculating section.
In such a prior-art fuel supply control system, since the pulse width of a fuel injection pulse is gradually increased for increase in fuel supplied into the engine cylinders when the engine is accelerated, an excessive vibration may be reduced in the engine; however, there exists another problem in that the engine torque is not quickly increased immediately after the engine is accelerated.